[PATCH v2 07/21] KVM: x86/mmu: Topup memory caches after walking GVA->GPA

Sean Christopherson
2020-06-22T20:11:44Z

Topup memory caches after walking the GVA->GPA translation during a
shadow page fault, there is no need to ensure the caches are full when
walking the GVA. As of commit f5a1e9f89504f ("KVM: MMU: remove call
to kvm_mmu_pte_write from walk_addr"), the FNAME(walk_addr) flow no
longer add rmaps via kvm_mmu_pte_write().

This avoids allocating memory in the case that the GVA is unmapped in
the guest, and also provides a paper trail of why/when the memory caches
need to be filled.

Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/mmu/paging_tmpl.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 38c576495048..3de32122f601 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -791,10 +791,6 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,

pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);

- r = mmu_topup_memory_caches(vcpu);
- if (r)
- return r;
-
/*
* If PFEC.RSVD is set, this is a shadow page fault.
* The bit needs to be cleared before walking guest page tables.
@@ -822,6 +818,10 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
return RET_PF_EMULATE;
}

+ r = mmu_topup_memory_caches(vcpu);
+ if (r)
+ return r;
+
vcpu->arch.write_fault_to_shadow_pgtable = false;

is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu,
--
2.26.0